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In recent years, synchronous reluctance (Syn-Rel) machines are research hotspots in variable speed motor drives due to their robust rotor structure and wide constant power speed range (CPSR). More practically, when kVA limitation is considered, embedded permanent magnets (PMs) have been widely adopted in Syn-Rel rotors to further increase power density as well as power factor. In this paper, the authors have investigated the potential of PM-assisted Syn-Rel machine to be the next generation electrical propulsion motor topology for automotive application, with special attention put on a key geometric parameter, i.e., airgap length. In MTPA region, the influence of airgap length on different torque components has been analyzed in detail based on the frozen permeability method. In field weakening region, the variation trend of several key performance such as peak power, iron loss and torque ripple have been investigated along with airgap length. It is found that with specifically high level of electric and magnetic loading, there exists optimal value of airgap length to achieve high power density based on specific cooling and kVA limitation. Numerical FEA and experimental tests are associated to validate the conclusions.

High power density and high torque density are the fundamental requirements for electric machines used in traction application. The former is obtained by potentially increasing the speed of the machine while the latter by using high energy density rare earth magnets. Ferrite magnets are explored as a viable alternative to rare earth magnets which are relatively expensive and geographically concentrated. The paper is intended to bring out the current trend of electric machines used in electric vehicles (EVs) with due focus on permanent magnet assisted synchronous reluctance (PM-SynRel) machine. High power and high speed PM-SynRel machine with rare earth and ferrite magnets are designed and compared based on the requirements for a future electric commercial vehicles. The ratio of stack length, mass of magnet, total mass and inertia of rare earth machine in comparison to ferrite PM-SynRel is found to be 0.72, 0.42, 0.72 and 0.32, respectively. Based on these, the rare earth based machine is found to have high power density, torque density and also utilizes lesser volume of magnets but PM-SynRel with ferrite is getting closer.

Electrical machines with high torque density are required for traction application. Availability of bonded magnets with complex shapes and magnetization pattern can significantly extend the design space of electrical machines. This paper introduces a hybrid flux barriers design to improve the torque density of permanent magnet assisted synchronous reluctance (PM -SynRel) machine using ferrite magnets. The torque density with hybrid flux barriers is found to improve along the entire range of speed compared to the conventional flux barriers. The hybrid barrier design achieves similar performance to that of curved barrier with relatively flat shaped magnets in the last flux barrier. Thus, the hybrid barrier is able to enhance the torque density at a potentially reduced cost of manufacturing. The hybrid flux barrier design is validated for both electromagnetic and mechanical performance using commercial finite element analysis (FEA) packages.

High-performance power conversion equipment is currently gaining an increasing interest for aircraft applications. In particular, isolated bidirectional dc/dc converters are often proposed for modern aircraft distribution systems. A current-fed isolated dc/dc converter, named active-clamp active-bridge topology, is identified as the most promising for the proposed application, interfacing a 270-V dc network with a 28-V dc network. A comparison between the selected topology and the well-known dual-active-bridge topology has been carried out and an experimental prototype has been manufactured for the selected conversion architecture. Simulation and experimental results are provided in order to validate the tradeoff and the design of the proposed converter.

In an electrical machine design, thermal management plays a key role in improving the performance and reducing size. End-windings are commonly identified as the machine hot-spot. Hence, lowering and predicting end-windings temperature are crucial tasks in thermal management of electrical machines. This paper proposes and investigates a noninvasive but effective cooling method that aims for a uniform cooling of a machine's winding by implementing direct cooling on its end-windings. Modeling and experimental results show that a 25% hot-spot temperature reduction on a particular application can be achieved. To analyze the proposed technique in detail, an accurate but computationally economic lumped parameter thermal network is developed. Comparison between a “standard” thermal network and its simplified equivalent (with less nodes) is presented where the models are developed and fine-tuned based on experimental data. All the above is used to investigate the potential of the proposed end-winding cooling method with different configurations of the methodology.

We summarise our experience developing and using Termite, the first reactive synthesis tool intended for use by software development practitioners. We identify the main barriers to making reactive synthesis accessible to software developers and describe the key features of Termite designed to overcome these barriers, including an imperative C-like specification language, an interactive source-level debugger, and a user-guided code generator. Based on our experience applying Termite to synthesising real-world reactive software, we identify several caveats of the practical use of the reactive synthesis technology. We hope that these findings will help define the agenda for future research on practical reactive synthesis., Comment: In Proceedings SYNT 2016, arXiv:1611.07178

High performance and reliable electrical machines are often required in modern applications and an appropriate thermal management allows to fulfil such demand. Thermal management is crucial for improving performance, reducing size and preserving the insulation lifetime of electrical machines. From this prospective, a novel cooling method for machine end-windings is proposed in the present work. Its cooling action focuses on the end-windings, since they are commonly identified as the machine hot-spot. The effectiveness of the proposed cooling method is experimentally proved and the improvement, in terms of current density, for a given wire insulation thermal class, is quantified. A previously designed permanent magnet synchronous machine, implementing a traditional housing water jacket, is used as a case study. The influence of the improved current density on machine torque density is investigated, through finite element simulations, when the proposed cooling method is integrated to the existing housing water jacket.

Electric vehicles (EVs) are rapidly becoming more common and ownership is set to rise globally in coming years. The potential impacts of increased EVs on the electrical grid have been widely investigated and in its current state, existing grid infrastructure will struggle to meet the high demands at peak charging hours. The limited range of electric cars compounds this issue. We therefore propose CognitiveCharge, a novel approach to predictive and adaptive disconnection aware opportunistic energy discovery and transfer for the smart vehicular charging. CognitiveCharge detects and reacts to individual nodes and network regions which are at risk of getting depleted by using implicit predictive hybrid contact and resources congestion heuristics. CognitiveCharge exploits localised relative utility based approach to adaptively offload the energy from parts of the network with energy surplus to depleting areas with non-uniform depletion rates. We evaluate CognitiveCharge using a multi-day traces for the city of San Francisco, USA and Nottingham, UK to compare against existing infrastructure across a range of metrics. CognitiveCharge successfully eliminates congestion at both ad hoc and infrastructure charging points, reduces the time that a vehicle must wait to charge from the point at which it identifies as being in need of energy, and drastically reduces the total number of nodes in need of energy over the evaluation period.

Converter sizes are often dominated by passive magnetic components. Passive magnetic component sizes are in turn limited by electromagnetic saturation and thermal limits. This paper covers two modifications to the air gaps of tape wound amorphous magnetic cores, made available by the advancement of additive manufacturing with magnetic materials. These are modifying the width of the core at the air gap and moving the air gap to a different location in the core. The objective was to reduce the effect of fringing flux, and to overcome the issue of a high loss zone and thermal hot spot being generated at the air gap, situated under the windings. These modifications will reduce temperatures and thus allow for smaller components before thermal limits are reached. The changes this causes to inductance, flux density and losses are highlighted and discussed.

This paper seeks to better understand the highly multi-dimensional, multi-faceted challenges of meeting trust and reliability requirements in critical, disaster aftermath communication networks comprising heterogeneous groups of sensor equipped nodes. Through emulation of a UK based flooding event in the South of England we show the impact of selfish and malicious nodes on disaster communications when disparate, distributed, and disconnected nodes are carrying sensitive messages relating to resource availability and need. To further support the need for trust-aware schemes in such environments we compare benchmark DTN protocols against our reliable, trust-aware framework, TACID, which penalises and excludes malicious nodes. We show that in disaster aftermath networks trust-aware schemes can significantly reduce the impact of malicious intermediary nodes and increase overall reliability whilst simultaneously maintaining message confidentiality.

High performance power conversion equipment is currently gaining an increasing interest for aircraft applications. In particular, isolated bidirectional DC/DC converters are often proposed for modern HVDC aircraft distribution systems. For such reason an evaluation of several isolated DC/DC converter topology is carried out considering the proposed application, interfacing a 270V DC network with a 28V DC network. A trade off evaluation has been carried out for three different topologies and an experimental prototype has been manufactured for the selected conversion architecture. Simulation and experimental results are provided in order to validate the trade off and the design of the proposed converter.

Video over vehicular networks continues to receive warranted attention, with envisioned applications having the potential to present entirely new opportunities and revolutionise existing services. Many video systems have been proposed, ranging from safety to advertising. We propose a novel system for VANETs, namely the TArgeted Remote Surveillance (TARS) module for the existing Greedy Perimeter Stateless Routing (GPSR) protocol which permits multiple mobile vehicles to request and receive live video feeds from vehicles within a select geographic region. The multi-hop, vehicle-to-vehicle system enables mobile units to surveil a target area in real time by leveraging the dashboard cameras of vehicles moving within the target region. We combine several proposed extensions to the core protocol to introduce a dynamic real time congestion aware clustering scheme to achieve this. Our proposed system is compared against existing routing protocols using mobility data from Nottingham. GPSR-TARS outperforms the protocols assessed in key criteria crucial for meeting the quality of service demands of live multimedia dissemination.

This paper details the design process of a high performance electrical machine with the objective of achieving US Department of Energy FreedomCar 2020 targets, namely meeting the high speed efficiency requirement without sacrificing performance elsewhere. The FreedomCar targets are detailed, with a short discussion of the challenges involved. All feasible machine topologies are considered, and qualitatively compared in order to identify the best candidate topologies. A set of potential technologies and topologies are evaluated to establish the primary geometry specifications, such as slot pole combination, winding layout and active length. Optimisation methods are then implemented to establish the more detailed geometrical parameters, e.g. tooth width and slot depth. Finally a conclusive design is presented with the finite element simulation results. The design meets all the performance requirements of the targets.

We introduce the reactive synthesis competition (SYNTCOMP), a long-term effort intended to stimulate and guide advances in the design and application of synthesis procedures for reactive systems. The first iteration of SYNTCOMP is based on the controller synthesis problem for finite-state systems and safety specifications. We provide an overview of this problem and existing approaches to solve it, and report on the design and results of the first SYNTCOMP. This includes the definition of the benchmark format, the collection of benchmarks, the rules of the competition, and the five synthesis tools that participated. We present and analyze the results of the competition and draw conclusions on the state of the art. Finally, we give an outlook on future directions of SYNTCOMP., Comment: 24 pages, published in STTT

We report on the design and results of the second reactive synthesis competition (SYNTCOMP 2015). We describe our extended benchmark library, with 6 completely new sets of benchmarks, and additional challenging instances for 4 of the benchmark sets that were already used in SYNTCOMP 2014. To enhance the analysis of experimental results, we introduce an extension of our benchmark format with meta-information, including a difficulty rating and a reference size for solutions. Tools are evaluated on a set of 250 benchmarks, selected to provide a good coverage of benchmarks from all classes and difficulties. We report on changes of the evaluation scheme and the experimental setup. Finally, we describe the entrants into SYNTCOMP 2015, as well as the results of our experimental evaluation. In our analysis, we emphasize progress over the tools that participated last year., Comment: In Proceedings SYNT 2015, arXiv:1602.00786